FR2616153A1 - THERMOSTABLE COPOLYMERS STRUCTURE SEQUENCES (IMIDE-AMIDE BLOCK) - (UREE-SILOXANE BLOCK) - Google Patents

Abstract

Novel thermally stable block copolymers containing (imide-amide) and (urea-siloxane) blocks. <??>More precisely, these copolymers are obtained by a chain sequence of the following two stages: - stage (a): preparation of an oligomer containing end N=C=O groups from an aromatic diisocyanate and a monoanhydride of an aromatic tricarboxylic acid, and - stage (b): reaction of the said oligomer with a diamine of formula: in which: X denotes: each of R1, R2, R3, R4 and R5 denotes a hydrocarbon radical, x is a number ranging from 2 to 8 and the sum y + z is between 0 and 100. <??>These copolymers are employed especially for the production of coating films.

Description

THERMOSTABLE COPOLYMERS STRUCTURAL SEQUENCES

  (IMIDE-AMIDE BLOCK) - (UREE-SILOXANE BLOCK)

  The present invention relates to thermostable copolymers

  sequences comprising (imide-amide) and (urea-siloxane) blocks.

  The combination of imide repeating units and / or amides and siloxanes has been advantageously employed in the preparation of polymers useful in insulating coating applications for which the coating must possess excellent thermal stability. A representative prior art that describes polymers of this nature is US Pat. No. 4,395,527. More specifically, this document provides poly (imide-amide) containing siloxane units which are the reaction product of a diorganopolysiloxane diamine with a tricarboxylic acid monoanhydride: CO

H2N - A - NH2 + HOOC - B O

Co \ "c / CO

-A - NH - CO - B N

Co n

  with A representing a diorganopolysiloxane divalent group.

  There are other documents describing thermostable polymers comprising imide units and / or amides and siloxanes (see in particular US-3,274,155, US-A-3,325,450, US-A-3,553,282, US-A- 4,011,279); however, in this prior art, the novel block copolymers according to the present invention are not disclosed.

  comprising (imide-amide) and (urea-siloxane) blocks.

  More specifically, the present invention relates to thenrostable block copolymers characterized by the following points: (1) they comprise in their structure: - 2 - - blocks (imide-amide) of formula: Co

D NH - CO - B N D (I)

  m in which: * D represents a single valency bond or a grouping: CH;

-CH -; - C-; -O -; S -; S-; H-C-Q;

CH3 O X

  B represents a trivalent radical consisting of a substituted or unsubstituted aromatic radical or in two of these radicals connected to each other by a single valency bond or a grouping:

- CH - - C - - O-; - C -

2 1 He

CH3 O

  m is a positive number equal to at least 1, and more precisely in the range of 1 to 10; and blocks (uresiloxane) of formula:

  NH - CO - NH - A - NH - CO - NH- (II)

  with A representing a divalent diorganosiloxane radical of formula:

R1 R2 R4 R1

  X - (CH 2) - Si -O i O Si-O Si- (CH 2) -x R 1 R Y R z R 1 R 3 R 5 z R 1 III)

-6 16153

  In which: X, which is in the ortho, meta or para position with respect to the carbon atom of the benzene ring bearing the valency bond, represents an atom or a following group:

- o -; - S - S- - S -

He I1

O O

  R1, R2, R3, R4 and R5, which are identical or different, each represent a monovalent hydrocarbon radical chosen from: linear or branched alkyl radicals having from 1 to 12 carbon atoms, these radicals being able to be substituted by one or more chlorine, bromine or fluorine atoms or by a group - CN; a phenyl radical optionally substituted by one or more alkyl and / or alkoxy radicals having from 1 to 4 carbon atoms or by one or more atoms

chlorine; -

  * the symbol x is an integer in the range of 2 to 8 '; * the symbols y and z represent numbers, identical or different, integer or fractional, whose sum is in the range from 0 to 100; (2) they are obtained by sequencing in the same reactor the following two steps: step (a) in which: an oligomer with terminal isocyanate groups is prepared by heating, at a temperature ranging from -50 ° C. to 200 ° C. and the presence of an organic solvent or mixture of organic solvents, the following reagents (i) and (2i): (i) was a diisocyanate of formula:

O = C = N D N = C = O (IV)

  wherein D has the meaning given above in the formula (I), and (2i) is a tricarboxylic acid monoanhydride of the formula: ## STR2 ## wherein B has the meaning given above in formula (I); the proportions of the reactants (i) and (2i) are chosen so that the ratio: number of moles of diisocyanate (i) number of moles of anhydride (2i) is in the range from 1.1 to 2 ; heating is carried out for a time sufficient to react all the functional groups of the anhydride (2i); step (b) in which: the reaction medium obtained at the end of step (a) containing the oligomer containing terminal isocyanate groups with (3i) is reacted at a temperature ranging from 50 ° C. to 160 ° C. ) a diamine diorganopolysiloxane group of formula: ## STR2 ## Si-Si-O-Si-OO Si- (CH2) -X R1 y ZR

<R _ R3 _ YR5 _ 1I

i (i VI)

NH2 NH2

  wherein X, R 1, R 2, R 3, R 4, R 5, x, y, and z have the meanings given above in formula (III); the proportions of the reagent (3i) are chosen so that the ratio: number number of moles of diamine siloxane (3i) number of moles of diisocyanate (i) - number of moles of anhydride (2i)

  is in the range of 0.5 to 1.

  With regard to the formula of the block copolymers according to the invention, it should be understood, if B 1 designates an (imide-amide) block of formula (I) and by B2 a block (urea-siloxane) of formula (II), that it is essentially the following:

4 B1 - B 2

  with p representing a positive number ranging from 1 to 100.

  By way of specific examples of diisocyanate (i) of formula (IV) which are particularly suitable, mention may be made in particular of: 4,4'-diphenyl-2,2-propane diisocyanate, 4,4'-diisocyanato diphenylmethane, 4,4'-biphenyl diisocyanato, 4,4'-diphenylsulfide diisocyanato, 4,4'-diphenylsulfone diisocyanato, 4,4'-diphenyl diisocyanato,

  4,4'-diphenyl-1,1-cyclohexane diisocyanato.

  4,4'-diphenylmethane diisocyanato and 4,4'-diphenyl ether diisocyanato are preferably used for the practice of the present invention. As specific examples of tricarboxylic acid monoanhydrides (2i) of formula (V) which are suitable, mention may be made in particular: trimellic acid monoanhydride, naphthalene acid monoanhydride-2,3 2,3,6-tricarboxylic acid, 1,8-naphthalene-1,8,4-tricarboxylic acid monoanhydride, 1,2-naphthalene-1,2,4-tricarboxylic acid monoanhydride, 3,4-diphenyltricarboxylic acid-3,4,4 'monoanhydride, 3,4-diphenylsulfonecarboxylic acid-3,4,3' monoanhydride, 3,4-monoanhydride, 3,4,4'-diphenyl ether tricarboxylic acid, 3,4-benzophenone tricarboxylic acid-3,4-monoanhydride,

  3,4-monoanhydride of diphenyl-isopropylidene acid

  3,4,3-tricarboxylic. Preferably used for the implementation of this

  invention, trimellic acid monoanhydride.

  With regard to the siloxane diamines (3i) of formula (VI), when y and / or z are greater than 1, it is in the presence of a compound & polymeric structure and there is seldom a single compound, but most often a mixture compounds with the same chemical structure, which differ in the number of repeating units of their molecule; this leads to an average value of y and / or z which can be integer or fractional. As preferentially representative diamines, mention may be made of those which correspond to formula (VI) in which: 1. X = -O-; R1, R2, R3, R4 and R5, which may be identical or different, each represent a linear or branched alkyl radical having from 1 to 6 carbon atoms; x = 2, 3, 4 or 5; y + z is in the range of 0 to 100 and preferably 4 to 70; 2. X = - O -; R1, R2, R3, which may be identical or different, each represent a linear or branched alkyl radical having from 1 to 6 carbon atoms; R4 and R5 each represent a phenyl radical; x = 2, 3, 4 or 5; y + z is in the range of 0 to 100 and preferably 4 to 70; 3. X = - O -; R1, R2, R4, which may be identical or different, each represent a linear or branched alkyl radical having from 1 to 6 carbon atoms; R3 and R5 each represent a phenyl radical; x = 2, 3, 4 or 5; y + z is in the range of from 0 to and preferably from 4 to 70; 4. X = - O -; R1 represents a linear or branched alkyl radical having from 1 to 6 carbon atoms; R2, R3, R4 and R5 each represent a phenyl radical; x = 2, 3, 4 or 5; y + z is in

  the range from 0 to 100 and preferably from 4 to 70.

  As even more preferentially representative diamines, mention may be made of those which correspond to formula (VI) in which: X = -O-; R1 = R2 = R3 = = R = R5 = linear alkyl radical having 1 to 3 carbon atoms; x = 2, 3 or 4; y + z is in the range of 0 to 100 and preferably 4 to 70; 6. X = - O -; R1 = R2 = R3 = linear alkyl radical having 1 to 3 carbon atoms; R4 = R5 phenyl radical; x = 2, 3 or 4; y + z is in the range of 0 to 100 and preferably 4 to 0; 7. X = - O -; R1 = R2 = R4 = linear alkyl radical having 1 to 3 carbon atoms; R3 = R5 = a phenyl radical; x = 2, 3 or 4; y + z is in the range of 0 to 100 and preferably 4 to 70; 8. X = - O -; R1 = linear alkyl having 1 to 3 carbon atoms; R2 = R3 = = = R5 = phenyl radical; x = 2, 3 or 4; y + z is located

  in the range of 0 to 100 and preferably 4 to 70.

  As diamines which are particularly representative, there may be mentioned those which correspond to the formula (VI) in which: X = -O-; R = R = R3 = R = R = methyl radical; x = 3; y +

I. 2 3 4 = 5

  z is in the range of 0 to 100 and preferably 4 to 70; 10. X = - O -; R1 = R2 = R3 = methyl radical; R4 = R5 = phenyl radical; x = 3; y + z is in the range of 0 to 100 and preferably 4 to 70; 11. X = - -; R1 = R2 = R4 = methyl radical; R3 = R5 = phenyl radical; x = 3; y + z is in the range of 0 to 100 and preferably 4 to 70; 12. X = - O -; R1 = methyl radical; R2 = R3 = R4 = R5 = phenyl radical; x = 3; y + z is in the range of 0 to 100

and preferably from 4 to 70.

  Specific examples of siloxane diamines that are particularly representative include:

CH CH CH

  13. o (CH2) -si - Osi - O si - (CH2) -

CH3 CH3 CH3

X CH3 _ C23 _ 3 0

o 20 to30Q -8-

CH3 CH3 CH

  14. 0 - (CH Si - O Si - O Si - (CH 2) 3 - O I I

CH3 CH3 CH

o where

NH_ NH2

2 NH2

CH CH ICH

1 3 1 3 1 3

15. if-o si- O si -o if

CH3 CH3 CH

3 c3 3 y z

(CH2) 3 (CH2) 3

O O

with y + z = 4 to 8

NH2 NH2

CH CH CH

1 1

CH3C3 oH3

N2 -NH2

  The diamines (3i) of the formula (VI) are preferably used for those in which the diorganopolysiloxane group contains both S-alkyl (or Si-substituted alkyl) linkages and Si-phenyl (or substituted Si-phenyl) linkages. Suitable compounds of this type are those belonging to the following groups, preferably in ascending order: compounds 2, 3 and 4, compounds 6, 7 and 8;

compounds 10, 11 and 12.

  The diamines (3i) of formula (VI) with a diorganopolysiloxane group are compounds which are well known in the prior art. They are for example described in the English patent

  GB-B-1,062,418 and in US Pat. No. 4,395,527.

  According to these documents, a first method for the preparation of these diamines, applicable in particular when it is possible to obtain a compound of formula (VI) oy = z = O, that is to say when a diamine with a grouping can be obtained diorganopolysiloxane, is to react a compound of formula N

H2N M

  X has the meaning given above and M is an alkali or alkaline earth metal, with a bis (haloalkyl) disiloxane of formula:

R1 R,

  Y - (CH2) x - Si - 0 - Si - (CH2) - Y

R R

  1 i o x has the value indicated above and Y is a chlorine atom, bromine or ioje, operating at a temperature between 20 and

    C in the presence of an aprotic polar solvent.

  In the case where it is desired to obtain a diamine (3i) of formula (VI) oy and / or z are different from zero, a second method of preparation taught by these documents consists in copolymerizing one mole of diamine with a diorganopolysiloxane group, prepared as indicated above, with an amount of one or more cyclic diorganopolysiloxanes capable of yielding moles of groups

- 10 -

  siloxy of formula: R2 - Si - O R3 and / or z moles of siloxy groups of formula: R 14 - - Si - O I R5 In general, the reaction is carried out at a temperature of between 80 and 250 ° C. a solvent and

  optionally a suitable catalyst.

  Another way of preparing the diamines (3i) of formula (VI), with y and / or z being equal to zero or different from zero, is to react with an ethylenically unsaturated compound of formula:

H N X (CH) CH CH

2 2 X-2 2

  wherein X, which is in the ortho, meta or para position with respect to the carbon atom of the benzene ring attached to the nitrogen, and x have the meanings given above, an alpha, omega-bis (hydrogen) diorganopolysiloxane of formula:

R R R _R

It 12 14 * 1 H- S - O i - o - o S- H

R 3 R5

  wherein R 1, R 2, R 3, R 4, R 5, y and z have the meanings given above. This hydrosilylation reaction is carried out by operating in bulk in the absence of a solvent and using a catalyst with

- 11 -

  platinum base. The alpha, omega-bis (hydrogen) diorganopolysiloxanes used are products that are well known in the silicone industry and are, for some, commercially available. They are for example described in French patents FR-A1-2,486,952 and

EN-A5-2.058.988.

  When one chooses to use this hydrosilylation reaction to prepare a diamine (3i) of formula (VI), the ethylenically unsaturated amine substrate which is well adapted to react with the alpha, omega-bis (hydrogen) diorganopolysiloxane consists in particular of an allyloxyaniline of formula:

O - CH

HN CH2

H2N H2

  Under these preferred conditions, we are thus led to diamines (3i) of formula (VI) where X = - O -, x = 3 and R1, R2, R3, R4, R5, y and z have general or precise meanings. data above. The reaction of step (a) of the process for preparing the copolymers according to the present invention is carried out in a homogeneous medium by adding to the reagents (i) and (2i) a solvent or mixture of solvents common to the reagents and the product. form. Suitable solvents are polar solvents, in particular N, N-dimethylacetamide, N, N-dimethylformamide, N-methylpyrrolidone-2, dimethylsulfoxide and a mixture of these solvents; they must be perfectly anhydrous. The polymerization reaction is carried out at a temperature of between 50.degree. C. and 200.degree. the best results are obtained at temperatures between 90 ° C. and 160 ° C. Preferably, the proportions of the reactants (i) and (2i) are chosen so that the ratio: number of moles of diisocyanate (i) number of moles of anhydride (2i) is in the range of 1.1 to 1.5. Generally, when

2 6 1 6 1 5

- 12 -

  a temperature of between 90 ° C. and 160 ° C. is used, all the functional groups of the anhydride (2i) have reacted after 2 to 3 hours. Practically, the starting reagents are dissolved in the solvent (s) possibly operating under heat, and then the solution obtained is brought to the desired temperature directly or

  gradually under normal pressure or under a suitable vacuum.

  In step (b), the siloxane diamine (3i) can be used as a solution in a solvent or a mixture of solvents such as those indicated above with respect to step (a). This second step is carried out at a temperature which is preferably between 90 ° C. and 120 ° C. More preferably, the proportions of diamine (3i) are chosen so that the ratio: number of moles of diamine siloxane (3i) ) moles of diisocyanate (i) - number of moles of anhydride (2i) is in the range of 0.65 to 0.95. Generally, when operating at a temperature of between 90.degree. C. and 120.degree. C., all of the amino groups reacted after 1 hour 30 minutes at

2 hours.

  At the end of step (b), the copolymer is obtained in the form of a solution. It can be precipitated by addition in the reaction medium of a nonsolvent or a mixture of non-solvents and separate the precipitated copolymer from the reaction medium. Suitable non-solvents are, for example, water, acetone, tetrahydrofuran, toluene or any other solvent which does not solubilize the desired copolymer. It is also possible to obtain the copolymer by evaporation of the solvent (s) of the medium

  reaction in a ventilated oven.

  These copolymers are well suited for the manufacture of fibers, coating films and insulating varnishes, for example.

  evaporation, or later.

  The examples that follow are given for illustrative purposes, but

non-limiting.

2 6 1 6 1 5 3

- 13 -

EXAMPLE 1

  1. Example of Implementation of the Present Invention: 1.1 Step (a): In a glass reactor, provided with an anchor-type stirrer and an ascending condenser, in which a slight excess pressure of dry nitrogen is established and which is preheated to 100 ° C. with the aid of a suitable oil bath, is introduced successively: 7 g (0.0365 mol) of trimellic acid monoanhydride, 11.9 g (0.0472 mol) ) diisocyanato4,4'-diphenyl ether, and

63 g of N-methyl-2-pyrrolidone.

  Allowed to react for 2 hours with stirring. At the end of this time, the reaction temperature is raised to 130 ° C and the

  reaction continue for a further 1 hour with stirring.

  The temperature of the reaction medium is then lowered to 100 ° C.

to implement step (b).

  Infrared spectrometry shows the presence in the reaction mixture of C = O imide bands at L = 1710-1,770 cm -1 and the absence of a C = O anhydride band at Y = 1850 cm -1 1.2 Step (b): Add up in the reaction medium obtained at the end of step (a) 9 g (0.0072 mol) of the diamine containing diorganopolysiloxane group which is described in paragraph 2 below, this diamine being used in the form of solution in 48.6 g of N-methyl-2-pyrrolidone. Allowed to react for 2 hours at 100 ° C.

and with stirring.

  The copolymer solution thus obtained is a dark red liquid mass having a weight of 136 g (it contains 24.7 g of copolymer). By infrared analysis, no primary amine is detected in the solution obtained; the rate of transformation of the

committed diamine is therefore 100%.

-616153

- 14 -

  The copolymer which has been prepared in the form of a solution comprises in its structure: blocks (imide-amide) of formula: ## STR1 ## and blocks (urea-siloxane) of formula:

CH CH CH

3 3 1 3

  0 - (CH 2) 3 - Si - 0 Si - 0 Si - (CH 2) 3 - 0

CH3 CH3

NH NH

l l

CO CO

NH NH

  The solution of the copolymer was used to coat a 5 cm long, desensitized type E glass braid. This impregnated braid

  is dried under a vacuum of 53.2 × 10 2 Pa and 120 ° C. for 12 hours.

  This braid is then subjected to a dynamic stress in torsion using a pendulum & fiber. The variation of the stiffness of the sample is thus measured as a function of the temperature, which makes it possible to determine the glass transition temperatures (Tg) of the material. The values obtained are the following: - Tg of the blocks (urea-siloxane): -40 C - Tg of the blocks (imide-amide): 160 C

  2. Description of the process for the preparation of diamine

  diorganopolysiloxane group used:

- 15 -

  This siloxane diamine has the following formula: ## STR3 ## wherein CH 2 (CH 2) 3 - Si - (CH 2) 3 - o

CH CH3

O

2NH NH2

  In a glass reactor equipped with a central stirrer, a dropping funnel and an ascending condenser in which a slight excess pressure of dry nitrogen is established, 346.3 g (0.37 mol) of an alpha, omega bis (hydrogen) polysiloxane of formula:

CH CH CH

ICH3 1 3 l 3 H - Si - O si - si - H

I I

CH CH

  having a molecular weight of the order of 936 g.

  The reactor is then introduced into a preheated oil bath at 55 ° C., and then the catalyst is added. The latter is the catalyst of Karsted (complex based on elemental platinum and ligands 1,3-divinyl tetramethyl-1,3,3,3 disiloxane): it is in solution in toluene (concentration of 3.5% by weight 2.05 cm 3 of this catalyst solution are introduced with a syringe; the ratio r (elemental platinum weight engaged / weight of the reaction mass) is 130.10-6. 110.3 g (0.74 mol) of metaallyloxyaniline are then gradually poured into the reactor for a period of 60 minutes, in order to control the exothermicity of the reaction. Thirty minutes after the end of the casting, it returns to an ambient temperature. The product obtained, weighing 456.5 g, is a clear, orange-brown, viscous oil having a proton NMR spectrum consistent with the diamine structure given above. Molecular mass

Z616153

-16 -

is of the order of 1248 g.

EXAMPLE 2

  1. Step (a): Into the reactor used in Example 1, are introduced successively at 100 C: - 11.9 g (0.062 mol) trimellic acid monoanhydride, - 18.1 g (0.0718 mol) ) diisocyanato-4,4'-diphenyl ether, and

70 g of N-methyl-2-pyrrolidone.

  Allowed to react for 1 hour at 100 ° C., then for 1 hour at 125 ° C. and for 1 hour at 150 ° C. The temperature is then lowered to 1000 ° C.

  view of the implementation of step (b).

  By infrared spectrometry, as in Example 1, the presence in the reaction mixture of C = oimide bands at & = 1710-1,770 cm -1 and the absence of a strip were noted.

C = O anhydride at = 1850 cm -1

  2. Step (b): 10 g (0.0080 mol) of the diorganopolysiloxane diamine, which is described above in the example, is added to the reaction mixture obtained at the end of step (a). 1, this diamine being also used as a solution in 90 g of N-methyl-pyrrolidone-2. It is allowed to react, with stirring, for 2 hours at 100 ° C. The copolymer solution thus obtained is a dark red liquid mass having a weight of 194 g (it contains 34.5 g of copolymer). Here again the degree of transformation of the diamine

is 100%.

  The copolymer which has been prepared in the form of a solution comprises in its structure: blocks (imide-amide) of formula:

- 17 -

Co

N O

0 NH -CO CO

  and blocks (urea-siloxane) of formula:

* CH CH CH

2H3 31 2 3

CH3 33

NH SH

I.I-

CO CO

  h4H NH The Tg values of the copolymer, measured as indicated in Example 1, are as follows: Tg of the blocks (urea-siloxane): -40 ° C. Tg of the blocks (imide-amide): 210 ° C.

  A film is prepared from the solution of the copolymer obtained.

  The solution is poured onto a glass plate in a 0.4 mm thick layer. The plate is put in an oven and heated to 100 C under a

  vacuum of 53.2.10 Pa for 12 hours.

  An opaque yellow film is obtained which is easily detached from the support and has the following tensile mechanical characteristics (measured according to the indications of the ASTM D 882 standard): - tensile modulus: 1200 MPa - resistance & failure: 65 MPa

- elongation at break: 35%.

- 18 -

Claims (5)

  1) themrostable block copolymers characterized by the following points: (1) they comprise in their structure: blocks (imideamide) of formula: Co X D Q NH- CO- B N Q D- Q (I)   Co m in which: * D represents a simple valency bond or a grouping: CH O CH; C; - O -; - S -; - S -; H - C 2 days I - D CH3 O   B represents a trivalent radical consisting of a substituted or unsubstituted aromatic radical or in two of these radicals connected to each other by a single valency bond or a grouping: CH 1 3 - CH -; - C -; - O -; - C -; 2 1l CH3 O   * m is a positive number equal to at least and blocks (urea-siloxane) of formula:   - NH - CO - NH - A - NH - CO - NH - (II)   with A representing a divalent diorganosiloxane radical of formula: - 19 - R R R R   j l 1 2 I 4X 1 x (CH2) x if o0 if 0 if 0- If (CH2 x R1 R3 y R5 - R1 CI3 (III)   wherein: X, which is in the ortho, meta or para position with respect to the carbon atom of the benzene ring bearing the valence bond, represents a following atom or group: - O -; - S -; - S -; - S -; I I1 O O   R1, R2, R3, R4 and R5, which are identical or different, each represent a monovalent hydrocarbon radical chosen from: linear or branched alkyl radicals having from 1 to 12 carbon atoms, these radicals being able to be substituted by one or more chlorine, bromine or fluorine atoms or by CN group; a phenyl radical optionally substituted with one or more alkyl and / or alkoxy radicals having 1 to 4 carbon atoms or with one or more chlorine atoms; * the symbol x is an integer located in the interval ranging from 2 to 8; -   * the symbols y and z represent numbers, identical or different, integer or fractional, whose sum is in the range from 0 to 100; (2) they are obtained by sequencing in the same reactor the following two steps: step (a) in which:   an oligomer with terminal isocyanate groups is prepared with   heating, at a temperature ranging from 50 ° C. to 200 ° C. and in the presence of an organic solvent or mixture of organic solvents, the following reagents (i) and (2i): (i) being a diisocyanate of formula: O = C = N D N = C = O (IV) 2 6 1 6 1 52   in which D has the meaning given above in formula (I), and (2i) being a tricarboxylic acid monoanhydride of formula: HOOC- B O (V)   CO in which B has the meaning given above in formula (2) * the proportions of the reactants (i) and (2i) are chosen so that the ratio: number of moles of diisocyanate (i) number of moles of anhydride (2i) is in the range of 1.1 to 2; heating is carried out for a time sufficient to react all the functional groups of the anhydride (2i); step (b) in which: the reaction medium obtained at the end of step (a) containing the oligomer / terminal isocyanate groups is reacted at a temperature ranging from 50 ° C. to 160 ° C. with (3i) ) a diamine & diorganopolysiloxane group of formula: R R R R   11 12 14 1 X - (CH 2) x - Si - 0 Si-O si - Si - (CH 2) - X L 1 t R 1 R 3 y R 5 z R 1 XI X (VI) NH2 NH2   wherein X, R1, R2, R3, R4, R5, x, y, and z have the meanings - 21 -   given above in formula (III) * the proportions of the reagent (3i) are chosen so that the ratio: number of moles of diamine siloxane (3i) number of moles of diisocyanate (i) - number of moles of anhydride (2i)   is in the range of 0.5 to 1.   2) Copolymers according to claim 1, characterized in that the diisocyanate (i) of formula (IV) is chosen from the group formed by: - 4,4'-diphenyl-2,2-propane diisocyanato, - diisocyanato 4,4'-diphenylmethane, 4,4'-biphenyl diisocyanato, 4,4'-diphenylsulfide diisocyanate, 4,4'-diphenylsulfone diisocyanato, 4,4'-diphenyl ether diisocyanate,   4,4'-diphenyl-1,1-cyclohexane diisocyanato.   3) Copolymers according to any one of claims 1 and 2,   characterized in that the tricarboxylic acid monoanhydride (2i) of the formula (V) is selected from the group consisting of: - trimellic acid monoanhydride, - 2,3-naphthalenetricarboxylic acid-2,3-monoanhydride, 6, 1,8-naphthalenetricarboxylic acid monoanhydride-1,8,4, 1,2,5-naphthalenetricarboxylic acid 1,2-monoanhydride, 3,4-diphenyltricarboxylic acid monoanhydride, 3,4,4 '- 3,4-diphenylsulfonetricarboxylic acid-3,4,3-monoanhydride, 3,4,4'-diphenylethertricarboxylic acid monoanhydride, 3-monoanhydride 3,4,4-benzaphenonetricarboxylic acid,   3,4-monoanhydride of diphenyl-isopropylidene acid 3,4,3-tricarboxylic.   4) Copolymers according to any one of claims 1 to 3,   characterized in that the diamines (3i) of formula - 22 -   (VI) those wherein the diorganopolysiloxane moiety contains both Si-alkyl (or Si-substituted alkyl) linkages and   Si-phenyl (or substituted Si-phenyl).   ) Copolymers according to claim 4, characterized in that the diamines (3i) used are those which correspond to the formula (VI) in which: X = - O -; R1, R2, R3, which may be identical or different, each represent a linear or branched alkyl radical having from 1 to 6 carbon atoms; R4 and R5 each represent a phenyl radical; x = 2, 3, 4 or 5; y + z is in the range of 0 to 100 and preferably 4 to 70; X = - O -; R1, R2, R4, which may be identical or different, each represent a linear or branched alkyl radical having from 1 to 6 carbon atoms; R3 and R5 each represent a phenyl radical; x = 2, 3, 4 or 5 represent; y + z is in the range of from 0 to and preferably from 4 to 70; X = - O -; R1 represents a linear or branched alkyl radical having from 1 to 6 carbon atoms; R2, R3, R4 and R5 each represent a phenyl radical; x = 2, 3, 4 or 5; y + z is in   the range from 0 to 100 and preferably from 4 to 70.   6) Copolymers according to any one of claims 1 to 4,   characterized in that the solvents used in step (c) and optionally in step (b) are N, N-dimethyl-acetamide,   N, N-dimethylformamide, N-methyl-pyrrolidone-2, dimethyl-   sulfoxide and a mixture of these solvents.